1. Field of the Invention
This invention relates to techniques for the continuous mixing, transporting and placing of large quantities of concrete as, for example, in building a dam.
2. Description of the Related Art
Concrete dams, for many years, have been built by mixing the various ingredients (aggregate, sand, Portland cement and water) in a mixing plant and transporting the concrete by rail cars to a cableway stretched across the dam. The concrete is carried in large buckets suspended from trucks which roll on the cable. The buckets are lowered into a serise of pours, called blocks, where the concrete is dumped from the bucket. By this procedure, pour rates as high as 200 yd.sup.3 /hr are achieved, but typically the rate is about 100 yd.sup.3 /hr. The cableways are disadvantageous because they sway in high winds and variably sag, depending upon how far the bucket is spaced from the edge of the canyon. They are, therefore, difficult to control.
Alternatively, at some dam sites, the mixed concrete has been transported to the dam site by trucks, dumped, and distributed by bulldozer.
It has been proposed previously in U.S. Pat. No. 3,845,631 (Malan) to build a dam by forming a pool upstream of the pool, and discharging the concrete from the mixing plant into the dam. All ingredients for the concrete are supplied to the mixing plant on floating conveyors. The pool is permitted to deepen as the dam rises, so that the mixing plant rises with the dam.